Marine Weather and Tide Forecast for Grosse Pointe Park, MI

AVIATION

Low pressure continues to slide east just south of the state line over northern IN/OH today. Morning shower band has largely pushed north of the area, save for some remnants over mbS, leaving areas of drizzle/mist in its wake. Cluster of showers and embedded thunderstorms is pushing northeast out of the Toledo area early this afternoon and is set to arrive near the Detroit terminals near or shortly after the start of the new forecast period. Unclear how well convection survives this far north as the warm front remains at the state border, but added a Prob30 for these southern terminals to highlight the lower-end potential. Otherwise, IFR/LIFR cloud hold firmly in place through tonight as periodic showers work across the area.

For DTW/D21 Convection... Convection that developed on the warm front over NW OH lifts near the airport this afternoon (~18-21Z).
The warm front, and better instability, remains at the state border so there's a fair amount of uncertainty how well thunder makes it this far north. Giving it the benefit of the doubt and added a Prob30 group to highlight the chance.

THRESHOLD PROBABILITIES...

* High for ceilings below 5000 feet today and tonight.

* Low to moderate potential for thunderstorms this afternoon, between roughly 18-21Z.

* Low for ceilings at or below 200ft this evening/tonight.

PREV DISCUSSION
Issued at 351 AM EDT Wed May 21 2025

DISCUSSION...

A stagnant upper air pattern takes shape today through the end of the week, with growing likelihood for the cool weather to persist even into early next week as persistent longwave troughing dominates the governing pattern. The process kicks off as a 500mb shortwave tracking into the northern Ohio Valley and its parent closed low over the eastern Dakotas shear out through the day. The attendant surface low center elongates just south of the Ohio stateline, sustaining moist and cool easterly flow across SE MI within its northern periphery. A band of showers along the 700mb moisture axis works northward early this morning before a transition to mostly drizzle into midday. Additional showers then fill in later today as the next wave of moisture and deformation slide up the frontal slope.

Good depth of moisture and PWAT around 1 inch will support occasional moderate rates, but poor lapse rates will generally limit prospects for thunderstorms and heavier rainfall. Will maintain a slight chance for thunder south of a line from Adrian to Port Huron where the 850mb warm sector nudging in brings slightly negative showalter indices this afternoon. The steadiest rain looks to set up near the Saginaw Valley where the elevated deformation axis pivots in place. Rainfall totals for most areas will range between one and three quarters of an inch, but some locations may exceed 1 inch. The latest HRRR offers a 30 to 50% probability for over 1 inch in the Saginaw Valley, and 10% or less elsewhere. All in all it will be a raw day, particularly in the Thumb and Tri-Cities where a biting 20 to 30 mph northeast wind off Lake Huron keeps temps in the lower 50s amidst the damp conditions. Elsewhere, wind will be weaker but highs will still struggle to reach the mid to upper 50s. These temps will be some 20 degrees below normal and may challenge the daily low max record at Flint (52 in 1986).

Additional light showers and drizzle work across the area tonight into Thursday as the surface low stalls over the Ontario peninsula.
Wind direction backs to northwest during the day tomorrow and becomes breezy to around 25 mph for the whole forecast area. As the low gradually releases east Thursday night, it pulls in 850mb temps around 0C along with some drier air that may allow for some breaks in the stratus by Friday. Despite better surface heating, temps will still be limited well below normal in this air mass. An upper low over northeast Ontario retrogrades across the Great Lakes during this period with additional scattered showers possible. This low then merges with the prior low over New England and stalls there through the weekend. This sets up continued northwest flow to perpetuate the thermal troughing. However, prospects for some more sun and air mass modification through the weekend should promote a slight warming trend back into the 60s.

MARINE...

A low pressure system reaches the northern Ohio Valley today. This sustains periods of rain and an uptick in winds/waves for the central Great Lakes. Small Craft Advisories drop-off for Lake St.
Clair and western Lake Erie later this morning while continuing into Thursday for the Lake Huron nearshore zones. Northeasterly gusts should climb into the upper 20 knot range along central Lake Huron and Saginaw Bay this afternoon with occasional wave heights in excess of 5 feet. Modest pressure gradient maintains 15-20 knot prevailing winds as the center of the surface low migrates into the eastern Great Lakes by this evening, backing winds toward the north.
The system will be slow to fully exit the vicinity which keeps additional opportunities for Small Craft Advisory conditions into Thursday night.

HYDROLOGY...

Most areas have received between a quarter and a half inch of rainfall over the past 24 hours. Numerous rain showers will continue to spread across the state today into tonight. From this morning through Thursday morning, additional rainfall amounts will range between one and three quarters of an inch, with localized areas possible to reach 1 inch. There is a 30 to 50 percent probability to exceed 1 inch in the Saginaw Valley. Given the long duration of rainfall and predominantly light rainfall rates, flooding is not anticipated apart from nuisance ponding where more moderate rainfall occurs.

DTX WATCHES/WARNINGS/ADVISORIES
MI...None.
Lake Huron...Small Craft Advisory until 10 PM EDT Thursday for LHZ421-422- 441>443.

Lake St Clair...None.
Michigan waters of Lake Erie...None.